Graphene quantum dots, RAM, and 3D printing

Graphene technology is progressing towards new applications while still keeping the interest on a basic level, as evidenced by the colorful array of most recent research results. Researchers have managed to use graphene for better RAM memory, to enhance quantum dots, and to demonstrate the potential of graphene for nanoscale 3D printing.

Quantum dots (QDs) are tiny light sources, typically made of semiconductor crystals with nanoscale dimensions. The sources rely on internal electronic transitions which emit a stream of photons, with the color defined by the QD material, shape, and size. To get light out of a QD, one first needs to shine light of a different color on them. The conversion of one color to another has not been extremely efficient, making for very low-intensity light sources. Now, researchers have constructed graphene QDs, showing that their brightness is five times better than that of classical QDs. The brightness of a QD plays a role in, for example, medical applications, where QDs are used to highlight cancer cells in the body.

Published in the journal Nanoscale, the research shows that graphene QDs have a large surface area, increasing the interaction area between light and the material. What's even better, the bright dots are made of carbon, which means they are probably non-toxic and biodegradable.

Image: Quantum dots made of graphene are brighter than conventional counterparts (Brookhaven National Laboratory).

Health technology is one of the most prominent contemporary research directions. In parallel, large efforts are still being directed towards enhancing computer power and speed. Graphene has something to offer on that front as well, as exemplified by the most recent research on graphene RAM.

RAM memory has been evolving along with other parts of the computer. A well known property of RAM is its volatility - the fact that the memory is cleared when the power is shut down. Along with improving the speed and robustness of RAM, efforts are being undertaken to develop non-volatile RAM, i.e. one that would not lose data when the computer is shut down. Recent technological developments include carbon nanotubes and the magnetic tunnel effect.

Now, a ferroelectric tunnel junction based on graphene and ammonia has been shown to act as non-volatile RAM. In this device, graphene acts as an efficient electrode, covering the active ammonia layer. Simultaneously, graphene serves to protect the atomically-thin ammonia layer from the environment. In addition, the on/off ratio of the graphene/ammonia RAM is better than existing RAM.

On a more fundamental level, graphene plays a role as an enabling technology for 3D printing. In a recent turn of events, a team of scientists from Korea has demonstrated printing of nanostructures from graphene. For the first time, we have witnessed 3-dimensional structures made entirely from graphene, printed with a novel process. The process consists of dispersing a graphene oxide (GO) solution in a micropipette, depositing the solution locally, then reducing the GO to graphene. The following video shows a recording of a graphene nanowire bridge, constructed with this new method.

The resolution of the printer is about 150nm.

To learn more about graphene, stay tuned for the free online graphene course, to be offered by Chalmers University at the beginning of 2015.